System and method for achieving planar alignment of a substrate during solder ball mounting for use in semiconductor fabrication

ABSTRACT

A system ( 10 ) and method ( 30 ) for precisely depositing a solder compound onto a substrate ( 18 ). The system ( 10 ) generally includes a receiving member ( 20 ) having a rotatable portion ( 21 ) adapted to receive a planar substrate ( 18 ), a horizontal member ( 12 ) for depositing solder balls ( 11 ) on the substrate ( 18 ), and a contact member ( 14 ), located between the receiving member ( 20 ) and horizontal member ( 12 ). The contact member comprises an aligner plate ( 14 ) having a pair of stoppers ( 15 ) protruding therefrom. Advantageously, pivotable portion ( 21 ) of the system ( 10 ) establishes the planarity of the substrate ( 18 ), with respect to the horizontal mount ( 12 ) allowing for the solder balls ( 11 ) to be mounted thereon, preventing the substrate ( 18 ) from being slightly misaligned, warped, and/or tilted.

CLAIM OF PRIORITY

This application claims priority of U.S. Provisional patent applicationSer. No. 60/343,936 filed Dec. 28, 2001 entitled “System and Method forAchieving Planar Alignment of a Substrate During Solder Ball Mountingfor Use in Semiconductor Fabrication”

FIELD OF THE INVENTION

The present invention relates generally to semiconductor packaging andassembly and, more particularly, to a method and system for achievingplanar alignment of a substrate during solder ball mounting.

BACKGROUND OF THE INVENTION

Improvements in semiconductor packaging and assembly are rapidly beingmade by semiconductor manufacturers with the overall goal of increasingproductivity while reducing material waste. These improvements typicallyresult in semiconductor products that can be produced more cheaply andin greater quantity.

The actual process of packaging and assembling semiconductor productsusually involves a series of steps. One such step, such as for packagingflip chips, involves positioning a substrate-type material on aspecially designed movable support for receiving a solder, such assolder balls, from a solder depositing member. In operation, once thesubstrate has been positioned, the solder is then carefully depositedthereon. Conventionally, the substrate is sometimes misaligned or tiltedwith respect to the solder member, during the deposition of solderballs, which leads to the inaccurate placement of solder, the wastethereof, and decreased yields.

Accordingly, there exists a need for a semiconductor packaging andassembling method and system that stabilizes, with great precision, asubstrate material positioned on a moveable fixture with respect to thesolder depositing member during the application of the solder balls.This system would advantageously allow for positioning of the substrate,making it less sensitive to tilting and warping as the solder isdeposited thereon. Advantageously the system would also maintain theplanar alignment of the substrate, with the solder mounted thereon, asit is moved from one stage in packaging and assembly process to another.

SUMMARY OF THE INVENTION

The present invention achieves technical advantages as a system andmethod capable of allowing solder to be mounted on a substrate withgreater precision even if the substrate is slightly misaligned, warped,or tilted. Thus, rather than relying on the planarity of the substratestanding alone as it sits on a retractable support, the inventionprovides a pivotable substrate support which allows for mounting of thesoldering compound to occur by firmly dictating the angle of planarityof the substrate before and after the solder is deposited thereon.

In one embodiment the present invention is a system used to preciselydeposit a compound on a substrate, such as solder balls applied to aflip chip. The system generally includes a receiving member having apivotable portion which comprises a rotating vacuum coupling. Thereceiving member is adapted to hold a generally planar substrate. Thesystem also includes a horizontal member, comprising a ball mount, fordepositing solder balls on the substrate. To fix the planarity of thesubstrate as the solder ball are deposited thereon, the inventionincludes a contact member located between the receiving member and thehorizontal member to secure the substrate during attachment of thesolder balls. The contact member, comprising an aligner plate, hasstoppers protruding therefrom, such that the stoppers, together with therotating action of the vacuum coupling, combine to firmly fix thesubstrate in a substantially planar position before and after the solderballs are deposited thereon.

In another embodiment, the invention is a method of setting theplanarity of a substrate with respect to the solder ball apparatusbefore and after a solder is deposited thereon. The method generallybegins with the act of positioning a substrate on a receiving memberwhich has a rotatable portion, and is then followed by contacting andsecuring the substrate with a fixed contact member, comprising analigner plate having protruding stoppers, that establishes the planaralignment of the substrate before and after the solder is depositedthereon.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the invention and the specific embodiments will beunderstood by those of ordinary skill in the art by reference to thefollowing detailed description of preferred embodiments taken inconjunction with the drawings, in which:

FIGS. 1A, 1B and 1C show a rotating vacuum coupling and an aligner plateestablishing the planarity of the substrate in accordance with anexemplary embodiment of present invention;

FIGS. 2A and 2B show a top and side view, respectively, of asemiconductor fabrication system in accordance with the presentinvention;

FIG. 3 shows a solder ball attaching and depositing process inaccordance with the present invention; and

FIG. 4 illustrates a method of horizontally aligning the generallyplanar substrate using a receiving member having a rotating vacuumcoupling and aligner plates having a plurality of stoppers protrudingtherefrom according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The numerous innovative teachings of the present applications will bedescribed with particular reference to the presently preferred exemplaryembodiments. However, it should be understood that this class ofembodiments provides only a few examples of the many advantageous usesand innovative teachings herein. In general, statements made in thespecification of the present application do not necessarily delimit anyof the various claimed inventions. Moreover, some statements may applyto some inventive features, but not to others.

FIG. 1A shows a semiconductor fabrication system 10 in accordance withan exemplary embodiment of present invention. The system 10 is seen tohave a horizontal member 12 opposite a receiving member 20 which has asubstrate material 18 mounted thereon. The horizontal member 12comprises a solder ball mount apparatus, which is seen having aplurality of detachable solder balls 11,13 attached thereto. The solderballs are held in place by a plurality of spaced apart tool heads 44(not shown) which function to hold and selectively release the solderballs 11,13 above and upon the upper surface of substrate 18 atpredetermined locations, as will be discussed shortly in regards to FIG.3.

The system 10 also includes a receiving member 20 comprising asupporting base 19 and a vertical member 26 rotatably coupled thereto,forming a T-shaped support, and adapted to position and hold thesubstrate 18 opposite the horizontal member 12 in a planar relationshiprelative to the solder ball mount apparatus 12. In operation, thevertical member 26 contacts and supports the underside of the base 19and holds both the base 19, and the substrate 18 thereon, in placethrough vacuum pressure (i.e., suction) communicated therethrough toprevent the substrate 18 from undesirably shifting across the surfacethereof.

In a preferred embodiment, vertical member 26 which comprises a verticalvacuum conduit extended therethrough coupled to a vacuum source (notshown), is seen having a rotatable vacuum coupling 21 including topmember 22 and a bottom member 24 portion with a rotating vacuuminterface 23 pivotally coupled therebetween. As such, the rotatingvacuum interface 23 advantageously allows the base 19 to pivot invarying positions with respect to solder apparatus 12, causing, in turn,the substrate 18 fixed thereon to swivel slightly as base 19 andvertical member 26 each moves, up and down, along a vertical axisproximate attachment space 16 while remaining planar.

As shown in FIG. 1B, the ball mount 12 and the receiving member 20converge, and the soldering balls positioned therebetween are depositedon the substrate 18. An aligner plate 14 is shown evenly positionedbetween the horizontal member 12 and the receiving member 20. Moreover,aligner plate 14 is seen having two protruding portions comprisingstoppers 15 and 17 which are adapted to contact and secure with theouter edges of the planar substrate 18 as the base 19 is moved by member26, upwardly, into a receiving position therewith. Advantageously, therotating vacuum coupling 23 of the vertical member 26, along withstoppers 15 and 17, establish, with precision, the horizontal planarityof the substrate 18 and with respect to receiving member 20 such thatthe soldering balls 11,13 may be deposited thereon even if it ismisaligned, tilted or warped, prior to or during delivery of the solderballs.

With reference to FIG. 1C, there is shown the substrate 18 having solderballs 11, 13 uniformly positioned thereon and as deposited by horizontalmember 12 in accordance with an exemplary embodiment of the presentinvention. Stoppers 15 and 17 will remain in contact with the substrate18 after the solder balls 11,13 have been deposited thereon whilehorizontal member 12 retracts, and until both the base 19 and thevertical member 26 retract, simultaneously, along a vertical axis.Thereafter, the substrate 18 is then repositioned onto a movable tray 48and advanced for further processing. In addition, it should beunderstood that the aligner plate 14 may be adjusted so as toaccommodate substrate materials of varying lengths, shapes and sizes.Moreover, although the aligner plate 14 is seen having two stoppersprotruding therefrom and contacting the outer edges of the generallyplanar substrate 18, any number of stoppers may be designed into thealigner plate 14 to further stabilize and set the planar alignment ofthe substrate 18, such as, 4 or 6 stoppers, for example.

FIGS. 2A and 2B show a top and side view, respectively, of asemiconductor fabrication system. In one preferred embodiment, thealigner plate 14 is seen having a plurality of evenly spacedsquare-shaped openings 16, each having multiple protruding stoppers 15and 17. Moreover, each opening is adapted to receive multiple substrate18 units with respective vacuum apparatus 21 operatively positionedthereunder. The trays carrying the substrates 18 are advanced to theball attach station for applying the balls as previously described, andthen the tray of substrates 18, with the solder balls attached thereto,advanced.

FIG. 3 shows a solder ball attachment and depositing process inaccordance with the present invention. In one embodiment, the ball mountholder 12 comprises a plurality of tool heads 44 each adapted toindividually collect each solder ball 11,13 from solder bin 42 proximatea flux table 38. In operation, the tool heads 44 generate vacuumpressure, creating a suction force, to hold and remove the solder balls11,13 from the solder bin 42, whereby the solder balls 11,13 are thenmoved to a flux table 38 and dipped in a flux compound 40 before beingdeposited onto the substrate 18. During fabrication, a vision sensor 46is then used to sense if the solder balls 11,13 have been successfullyplaced on the substrate 18.

Referring now to FIG. 4, there is illustrated a method of setting theplanar alignment of the substrate 18 with respect to the solder ballapparatus 12 as applied in semiconductor fabrication in accordance withthe invention. The method, generally denoted as 30, begins with apositioning act 32 which involves positioning the substrate 18 on themovable receiving member 20 comprising the base 19 and the verticalmember 26 having the pivotable portion 21. In one embodiment, thepivotable portion 21 rotates the vacuum coupling 23 which is adapted torotate in a variety of different dimensions, causing, in turn, the base19, with the substrate 18 couple thereto, to rotate to make substrate 18planar with respect to horizontal number 12. Moreover, the receivingmember 20 is capable of moving linearly along a vertical axis.

Next, the positioning act 32 is followed by a holding act 34 wherein thesubstrate is elevated by member 26 to engage spaced apart stopper 15 and17 which contact the outer edges of substrate 18. In one preferredembodiment, the contact member, comprising the aligner plate 14, has twoprotruding stoppers 15 and 17, respectively. In operation, stoppers 15and 17 are adapted to lock in the angle of planarity of the substrate 18when it is elevated to a predetermined position by receiving member 20.

Finally, the holding act 34 is followed by a depositing act 36 whereinthe movable horizontal member 12, deposits a solder compound on thesubstantially planar substrate 18. In one select embodiment, thecompound consist of solder balls 11 and 13 which are spaced apart andare linearly configured so as to be deposited uniformly across thesurface of the substrate 18. To ensure planar stability of the substrate18, each stopper will remain in contact with the substrate 18 even afterdelivery of the solder balls as the member 12 retracts.

Though the invention has been described with respect to specificpreferred embodiments, many variations and modifications will becomeapparent to those skilled in the art upon reading the presentapplication. It is therefore the intention that the appended claims beinterpreted as broadly as possible in view of the prior art to includeall such variations and modifications.

What is claimed is:
 1. A method of depositing a solder onto a substrate,comprising the steps of: positioning said substrate on a receivingmember having a pivotable portion, said pivotable receiving membercomprising a portion adapted to act as an air conduit for holding saidsubstrate on said base; engaging said substrate with a contact member,whereby the pivotable receiving member establishes planarity of saidsubstrate with respect to said contact member; and depositing solder onsaid substrate.
 2. The method of claim 1 wherein said contact member hasprotruding side portions, said protruding side portions forming stoppersadapted to stop said substrate at a predetermined position with respectto such receiving member.
 3. The method of claim 1 wherein contactmember comprises an aligner plate opposing said pivotable receivingmember.
 4. The method of claim 1 wherein said pivoting receiving membercomprises: a base; a vertical member pivotably coupled to said base anddefining a T-shaped support, wherein said vertical member is adapted toact as said air conduit for holding said substrate on said base.
 5. Themethod of claim 1 wherein said pivotable receiving member comprises: atop portion; a bottom portion; and a pivotable member coupled betweensaid top and bottom portion, wherein said pivotable portion is rotatablein a plurality of different dimensions.
 6. The method of claim 1 whereinsaid solder ball mount configures a plurality of linearly configuredsoldering balls.
 7. The method of claim 4 wherein said pivoting verticalmember is a pivotable vacuum.
 8. A method of depositing solder onto asubstrate, comprising the steps of: mounting said substrate on apivotable vacuum member; providing an aligner plate; using saidpivotable vacuum member to press said substrate onto said aligner plate;and depositing solder onto said substrate.
 9. The method of claim 8,wherein said pivotable vacuum member comprises: a base; a verticalmember pivotably coupled to said base and defining a T-shaped support,wherein said vertical member is adapted to act as an air conduit forholding said substrate on said base.
 10. The method of claim 8, whereinsaid pivotable vacuum member comprises: a top portion; a bottom portion;and a pivotable member coupled between said top and bottom portion,wherein said pivotable portion is rotatable in a plurality of differentdimensions.
 11. A method of depositing solder onto a substrate,comprising the steps of: mounting said substrate on a pivotable vacuummember; providing an aligner plate; providing a horizontal memberaligned with said aligner plate; mounting solder on said horizontalmember; using said pivotable vacuum member to press said substrate ontosaid aligner plate; moving said horizontal member toward said alignerplate until said solder on said horizontal member contacts saidsubstrate.
 12. The method of claim 11, wherein said pivotable vacuummember comprises: a base; a vertical member pivotably coupled to saidbase and defining a T-shaped support, wherein said vertical member isadapted to act as an air conduit for holding said substrate on saidbase.
 13. The method of claim 11, wherein said pivotable vacuum membercomprises: a top portion; a bottom portion; and a pivotable membercoupled between said top and bottom portion, wherein said pivotableportion is rotatable in a plurality of different dimensions.